1. Field of Invention
The present invention relates, in general, to a photographic printing method and apparatus for producing three-dimensional (3D) pictures on lenticular print material. More specifically, it relates to a 3D printer which uses a video monitor for exposure.
2. Prior Art
In lenticular 3D photography, the basic process involves taking a plurality of two-dimensional (2D) images of a scene from a number of horizontally-spaced vantage points, and exposing the 2D images on lenticular print material, through one or more projection lenses, at different projection angles. It is well-known that lenticular print material is made of a lenticular screen coated with or attached to photosensitive emulsion, and a lenticular screen is a transparent sheet embossed with a contiguous array of semi-cylindrical lenses, or lenticules. When a series of 2D images are exposed through the lenticular screen, these 2D images are optically compressed to become line-form images. It should be kept in mind that a 3D picture is composed of 2D images of slightly different views of a scene, therefore, these 2D images must be accurately aligned with each other in reference to a common point in the scene. This reference point is known as the key subject in 3D photography and the alignment process is usually referred to as the key subject alignment.
Various techniques for exposing a series of 2D images onto lenticular print material have been disclosed in the past. U.S. Pat. No. 4,120,562 (Lo et al.) discloses a scanning method which uses an apparatus for changing the projection angles to properly fill the lenticules. U.S. Pat. No. 5,028,950 (Fritsch) discloses a dual-stage printer comprising an editing station and a printing station. In this disclosed dual-stage printer, the key subject locations in the 2D image frames are determined in the editing station while the exposing is carried out in the printing station. U.S. Pat. No. 5,036,356 (Lo) discloses a multi-lens camera preloaded with a roll of film on which a set of target images are exposed to assist key subject alignment.
Presently, in order to produce a 3D picture, it is necessary to take a series of 2D images and record these images on film. During printing, the 2D views recorded on film, or 2D negatives, are separately brought to an exposing position under the lamphouse in a 3D printer so that the images on the 2D negatives are separately projected through a projection lens onto a lenticular print material. It is understood that the print material and the projection lens must be moved to different positions in relation to the exposing position so that each 2D image is projected at a different projection angle. Furthermore, prior to exposure, the position of each 2D negative must be separately adjusted by mechanical means so that the key subject image in each 2D view can be precisely aligned with each other on the print material. Thus, in order to achieve a good registration of 2D views on a 3D picture, a conventional 3D printer must be equipped with a complex optical and computational device for locating the exact location of key subject in each 2D view; and a precise mechanical assembly for separately adjusting the position of each 2D negative at the exposing position under the lamphouse.
It is desirable to provide a 3D printer in which the key subject alignment process is greatly simplified, and the mechanical means for adjusting the 2D negatives is eliminated.